Grimmia tortuosa Hook.

13. Grimmia tortuosa Hook. f. & Wilson

in London J. Bot. 3: 540. 1844

(Fig. 15).

Lectoypus (designated by Muñoz, 1999: 174): United Kingdom. Falkland Islands Dependencies: “ Antarct. Exp. 1938-1843”, s.d., Hooker s.n. (BM [BM001007061]!; isolecto-: NY [NY01162773]!).

Gametophyte. Monoicous (fide Cao & Churchill, 1995 and Muñoz, 1999). Neither sporophytes nor perigonia seen. Growth form: cushions dense, compact, adherent to substrate by smooth rhizoids, plants sap green, radiculose at base, ascending, branched, stems up to 10 mm high, central strand well-developed or not at all, with intermediate states on one and the same stem. Leaves on lower part of stem muticous, 0.3- 1.0 mm long, suddenly becomimg markedly longer, up to 2-3 mm long, crowded, contorted, forming comal tuft when dry, scarcely moving when moistened, erecto-patent, stiff when wet, from elongate leaf base lanceolate, tapering to acute or obtuse apex, hair-point of different lengths, bluntly denticulate; leaf form in situ, at insertion and in leaf base concave, in transitional part widely keeled, in lower laminal part keeled, in upper laminal part narrowly or very narrowly so, margins plane throughout; basal cells hyaline, elongate-rectangular, longitudinal and transverse walls of even thickness, thin and smooth, scarcely nodulose, towards margin the hyaline cell rows gradually vanishing, outermost row reaching up to the broadest part of leaf, thus forming between hyaline basal cells and thicker walled chlorophyllose lamina cells a more or less well expressed delimitation, running obliquely from costa to margin, lamina cells isodiametric, lumina rounded; lamina, seen in transverse section, unistratose throughout, margin unistratose at leaf base, in upper half of leaf some cell rows bistratose or tristratose. Costa, seen on dorsal side, small at leaf base, markedly stout in laminal part, indistinct at apex, percurrent or excurrent to hair-point, seen in transverse section, at insertion and leaf base rounded, from there up to apex prominent, on ventral side at insertion plane, in transitional zone widely channelled, in upper half of leaf narrowly channelled, from insertion up to below apical part 4 guide cells, in apical part 2 guide cells, at insertion and leaf base costa composed of nearly uniform substereids, transformed in laminal part to a large band of stereids, dorsal cells with large lumina, no hydroids seen throughout. Sporophyte. Not seen.

Diagnostic characters. – Gametophyte. Leaves with margins plane on both sides throughout. Costa in laminal part prominent, with a large band of stereids, and hydroids lacking.

Distribution, habitat and ecology. – Grimmia tortuosa is currently known only from the type locality in the Falkland Islands, and the locality newly reported here from the study area.

In South Africa and Lesotho (Fig. 2 F), Grimmia tortuosa is currently known from a single locality at 1,940 m on the Waiihoekberge, at the southern end of the Hex River Mountains, where it occurs on damp, hard, quartzitic sandstone slabs in a shallow ravine where snow occasionally lies in late winter. Other species associated with it (e.g. Blindia magellanica Müll. Hal., Platyneurum praealtum (Mitt.) Ochyra & Bednarek- Ochyra) also exhibit similar disjunctive distributions.

Notes. – The description here is based on a unique, sterile specimen (Hedderson 14459, BOL). The descriptions given by Cao & Churchill (1995) and Muñoz (1999) as well as the protologue in Hooker & Wilson (1844) have also been taken into consideration for the description. Although geographically incongruous, the plants from South Africa match with both the description and the types of G. tortuosa, including the distinctive characters of a costa that is exceptionally rich in stereids below the middle of the leaf (see Fig. 15 E).

Specimen examined. – South AfriCA. Prov. Western Cape: Ceres area, Waaihoek Berge, Waaihoek Peak, c. 1940 m, 33°28’15”S 19°18’54”E, 18.III.2002, Hedderson 14459 (BOL).